Steam generator reheater



1936. D. J. MOSSHART ET AL 2,064,444

STEAM GENERATOR REHEATER File d Sept. 19, 1955 2 Sheets-Sheet l WITNESSES:

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L na 1936- D. J. MOSSHART E'T AL 2,064,444

S TEAM GENERATOR REHEATER Fil ed Sept. 19, 19:55 2 Sheets-Sheet 2 Fig.2,

14/ INVENTOR DONALD J. MOSSHHRT w in; g

0 0? w 1, J1 w 41m Jaw/2: and ROBERT A./ 5RSMRN a. a, M

ATTORNEY Patented Dec. 15, 1936 STEAM GENERATOR REHEATER Donald J. Mosshart, S

pringfield, and Robert A.

Foresman, Moores, Pa., assignors to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa. sylvania a corporation of Penn- Application September 19, 1933, Serial No. 690,162

2 Claims.

Our invention relates to steam power plants and it has for an object to provide improved means of heat utilization by the motive fluid.

With a plant where steam is delivered to the ,5 initial prime mover stage at high initial pressure and is expanded in prime mover stages down to the usual condenser vacuum, it is necessary, not only to superheat adequately the saturated steam on its way to the first prime mover stage, but also to reheat between stages to minimize condensation and to assure efficient conversion of heat energy into mechanical energy. Available materials of construction limit motive fluid temperatures, and we arrange that the temperatures of steam leaving the superheater as well as the reheaters shall be approximately the same. The latter result would be impossible of achievement where the superheating and reheating are accomplished by heating medium acting in serieson the superheater and reheater elements Without possibly using impractical designs; however, as we conduct the heating gases directly from the combustion or radiant heat chamber for passage in parallel through convection heat chambers containing these elements, adjust relatively the flow of heating gases therethrough,

and pass the gases in series through two or more.

chambers where desirable, our arrangement is flexible and each element may be heated to the so desired temperature. Accordingly, therefore, a

more specific object of our invention is to provide a power plant wherein steam is generated, superheated, and reheated between prime mover stages, superheating and reheating being accomplished by heating gases flowing from the combustion or radiant heat chamber through the convection in parallel together with the damper means for controlling the flow of gases through the convection heat chambers.

A further object of our invention is to pro-. vide a power plant including a structure defining a combustion chamber, a superheating chamber, and reheating chambers arranged in series in a horizontal row, heat being supplied from the combustion chamber to the upper portions of the superheating and reheating chambers and gases being delivered from the latter to an air preheater, air for the preheater passing through a duct arranged above the combustion, superheating and reheating chambers so as to insulate the 311 1 .61 part of the structure to make the latter a suitable supporting floor for the prime mover elements and heated air from the preheat r goin thmueh a d p vided in the structure underneath the various chambers and.

being supplied to the combustion apparatus arranged in the combustion chamber.

These and other objects are effected by our invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

.Fig. 1 is a longitudinal sectional view of our improved power plant; and

Fig. 2 is a sectional view taken along the line II..-II of Fig. 1.

In dealing with hi h pressure, for example, of the order of the critical pressure for steam, a very substantial pressure drop is required for a given heat drop. It is, therefore, desirable that the motive fluid shall not only be superheated to the desired point but that it shall be reheated between stages so as to get the maximum conversion of heat energy into mechanical energy and vto avoid -so far as .possible condensation of the motive fluid as it undergoes expansion. Accordingly, we provide for superheating and reheating of the motive fluid to substantially the same temperature, and this entails more and more superheating as the pressure is lowered. As already pointed out, to avoid having too unwieldy reheating elements, we utilize the heat and gases delivered from the combustion chamber in parallel in the superheating and reheating chambers, whereby the sizes of the reheat- ,ing elements are kept within reasonable limits. However, even with more and more superheating, superheating being limited by available materials of construction, we find that the reheaters should be increased in size as the pressure of motive fluid is reduced and its volume is increased.

Referring now to the drawings more in detail we provide a Structure In including structural steel frame .worlg, at ,l l, to provide an upper floor support --l2 for the multiple-stage prime mover, at I3, the structure having a combustion or radiant heat chamber 14, a superheater chamber .15 and reheater chambers 16, I7, and Hi, the chambers l5, l6, ll and 18 being referred to herein as convection heat chambers. The chambers M, l5, l6, l1 and iii are separated, respectively, by vertically extending walls I9, 20, 2|, and 22.

The structure 10 is .also provided with a horizontal supply passage 24 for supplying heating gases from the combution or radiant chamber M to the upper ends of the convection heat chambers, whereby the heating gases pass in parallel through the latter. ,A first discharge Similarly, motive passage 25 is arranged in the structure for receiving gases passing through the superheater chamber it? and the first and second reheater chambers H3 and ii. Both the supply passage 26 and the first discharge passage 25 discharge into the last reheater chamber 18, and gases leaving the latter enter the second discharge passage 21, which communicates with the air preheater as hereinafter more particularly described.

A motive fluid generating element or boiler 28 is arranged in the combustion chamber M, and the latter is provided with suitable combustion apparatus, at 29, for example, an oil or pulverized fuel burner.

A superheating element 33 is disposed in the superheating chamber l5, it is supplied with motive fluid from the generator 28 through the passage or conduit 3i, and it supplies superheated motive fluid through the conduit 32 to the first prime mover stage 33.

Motive fluid exhausting from the first prime mover stage 33 through the conduit 34 passes through the first reheater 35 and is returned by the conduit 3% to the second prime mover stage 31.

fluid exhausting from the second prime mover stage passes through the conduit 33 to the second reheater 39 and is returned by the conduit it to the third prime mover stage ll, and motive fluid exhausting from the latter through the conduit 42 goes to the third reheater 5 3, which supplies the last prime mover stage 55 exhausting to a condenser, not shown. The steam generator 23 is provided with an inlet 46 supplied with feed water in the usual way.

As will be seen from the drawings, the superheating andreheating elements are made successively larger, the element 35 being somewhat taller than the element 33, the element 39 being taller than the element 35 and the element 43 not only being taller than the preceding elements but being made of elbow shape in order to provide adequate surface. As already pointed out, the flow of heating gases from the combustion chamber iii in parallel through the superheating and reheating chambers provides for a high degree of reheating or superheating particularly in the last reheaters without using an unreasonably large amoimt of heating surface.

The flow of heating gases through the convection heat chambers for the superheater and reheater elements is proportioned and controlled by dampers, the dampers 41 controlling the passage through the superheater chamber IS, the dampers controlling the passage of heating gases through the first reheater chamber l6 and the dampers .9 controlling the passage of gases through second reheated chamber ll. Heating gases fiow in parallel through the last convection heat chamber for the reheater element 43 from the supply passage 24, the tubing of the element 43 being exposed, as shown at 53a, for the reception of such gases. Also, the tubing of the last reheater element 43 is exposed at the bottom, as indicated at 5!, to gases which have given up heat to the superheating and reheating elements 33, 35 and 39. Heating gases passing through the last reheater from either or both of these sources are delivered to the second discharge passage 2'i, dampers so and Ela. being provided for controlling communication between the last reheated chamber and the second discharge passage. As shown, the dampers 53 are positioned to control the direct passage across the reheater 43 of heating gases supplied from the supply passage 24 to the second discharge passage 21. By regulating the dampers 5B the heat given up to the last reheater elements 43 may be controlled as well as the proportioning of heat to the latter reheater element and to the other reheater and the superheater elements. The dampers 5la react on all of the elements to control the passage of gases therethrough, whereby the capacity of the plant may be raised and lowered. Also, the dampers 53 and Ella may be adjusted to secure more or less flow through the last reheater element in comparison to flow through the other reheater elements and the superheater. For example, if the damper 5la is partially closed, this will increase the resistance to flow from the supply passage 24 through the superheater and reheater elements 30, 35 and 39 and thence through the reheater element 43, this increased resistance tending to increase the direct passage of heating gases across the last reheater i3 and through the damper 53 to the second discharge passage. Thus, it will be seen that, by proper adjustment of the various dampers, each part of the installation may be caused to do its proper share and the installation as a whole my be controlled as determined by the power requirements.

Not only is the last reheater 43 made larger than the others for reasons already pointed out, but it will be seen that it is constructed and arranged to utilize heat derived from two sources, first, it operates in parallel with the other reheaters and with the superheater with respect to heating gases coming from the supply passage 21;, and, second, it operates in series with respect to gases which have passed in parallel through the superheater l5 and the first and second preheaters l6 and H.

The structural steel frame-work at H, is constructed and arranged to provide for the various combustion, superheating and reheating chambers arranged in line horizontally as well as the heating gases and air supply passages. To this end, the framework ll of the structure is comprised by steel columns 54 joined by cross beams 55, the columns and cross beams carrying a turbine or prime mover floor 56. Buckstays 51 are preferably arranged interiorly of the columns 54 and support suitable refractory structure for defining the heating chamber walls.

To increase the availability of the upper part of the structure to function as a prime mover, we preferably insulate such upper part by thecurrent of air used for combustion. To this end, we show a conduit 58 extending horizontally immediately below the cross beams 55 and over the combustion, superheating and reheating chambers, the conduit having an inlet 59 open to the atmosphere and discharging to the inlet of the forced draft blower 63, air going from the blower through the reheater 6| and. thence through the duct 62 arranged below the various combustion superheating and reheating chambers to the burner 29. Thus, it will be seen that the current of air passing through the duct 58 absorbs heat and serves to insulate the upper portion of the structure.

Combustion gases entering the second discharge passage 21 from the last reheater passed through the air preheater 6| and thence to the induced draft blower 63, for discharge to the stack 64.

As shown in Fig. 2, steam from the boiler and exhausted from the turbine elements 33 and 31, is supplied to header structure 66 communicating with several vertically disposed and parallel tube layers. At the upper portion of the superheater chamber l5 and of the first and second reheater chambers l6 and I7, the tubing extends upwardly, across, and downwardly and then communicates with outlet header structures, at 61, such arrangement of the tubing providing a heat-absorbing water-wall structure for the passage 24.

From the foregoing, it will be apparent that we have devised a power plant which is capable of generating motive fluid at a high pressure and effectively utilizing such fluid in converting heat and energy into mechanical energy, it being possible to assure that the superheater and reheaters shall discharge motive fluid or steam at approximately the same temperature. By way of example, if it is assumed that the temperatureof the steam leaving the superheater is 850 F. then to provide leaving temperatures for the first, second, and third reheaters that are about the same: if steam enters the first reheater at a temperature of the order of 750 F., it will be necessary to add of superheat in the first preheater; if steam enters the second reheater at a temperature of the order of 570, it will be necessary to superheat to the extent of 280; and if steam enters the last reheater at a temperature of the order of 370 F., it will be necessary to superheat tor the extent of 480 F. If the combustion gases passed in series through the superheater and the reheaters, the combustion gas temperature Would be successively lowered, thereby necessitating more and more heating surface to attain the desired discharge temperature; and this would entail unreasonably large structures for some of the heaters, particularly the low-pressure ones. On the other hand, parallel flow of gases through heaters and derived from a common source at high temperature level assures a more reasonable structural design. Furthermore, the provision of dampers makes it possible to proportion properly the application of heat to the superheating and reheating elements.

While we show what might be termed a generator or boiler in the combustion chamber, any suitable heater, irrespective of the physical state of the medium heated, may be located in such chamber. For example, with a boiler of the general type disclosed in U. S. Patent 1,740,254, December 17, 1929, the medium heated in the combustion chamber is saturated steam. Obviously, according to our invention, other heaters, such as reheaters, could be used with this boiler, such additional heaters being supplied with heat derived from gases passing in parallel therethrough and coming directly from the combustion chamber.

The chamber I4 is referred to herein as the radiant heat chamber for the reason that the heat absorbing elements associated therewith are heated mainly by radiant heat, although, of course, it is apparent that some heat absorption occurs due to contact or convection with the heated gases generated by the combustion means. The chambers I5, 16, I7 and it are referred to as convection heat chambers for the reason that heat absorption therein takes place entirely, or almost entirely, by contact or convection, it being understood that there may be some absorption of radiant heat in the chamber or chambers contiguous to the radiant heat chamber provided that the tubing thereof is not sufficiently screened to prevent the impingement of radiant rays thereon.

Therefore, our invention contemplates any multiplicity of motive fluid heaters where one may be heated in the combustion chamber and the others by heat derived from gases coming from the combustion chamber and passing in parallel therethrough.

While we have shown our invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What we claim is:

-1. In a steam generator comprising tubular means through which motive medium passes, a series of heating chambers including an initial radiant heat chamber and a final convection heat chamber with one or more intervening convection heat chambers, said chambers being arranged in parallel side-by-side relation and each of said chambers having a portion of the tubular means disposed therein, combustion means for supplying heat to the radiant heat chamber, a passage communicating with the radiant heat chamber and supplying heating gases issuing from the latter to the convection heat chambers for flow in parallel therethrough, an intermediate passage receiving heating gases issuing from the intervening convection heat chamber or chambers and discharging such gases into the final convection heat chamber at a point intermediate the length of the flow passage thereof,

an outlet passage for the final convection heat chamber, dampers between each intervening convection heat chamber and the intermediate passage, and dampers between the final convection heat chamber and the outlet passage and including a by-pass damper providing for gases by-passing at least a portion of the tubular means in the final convection heat chamber.

2. In a steam generator comprising tubular means through which motive medium passes, a

structure providing a plurality of heat chambers including an initial radiant heat chamber and a convection heat chamber with one or more intervening convection heat chambers, said chambers being disposed in vertical side-by-side relation and each chamber having a portion of the tubular means disposed therein, combustion means at the lower end of the radiant heat chamber, a horizontal passage communicating with the upper ends of the radiant heat chamber and of the convection heat chambers, an intermediate horizontal passage communicating with the lower end or ends of the intervening convection heat chamber or chambers and communicating with an intermediate portion of the final convection heat chamber, dampers for controlling communication of each of the intervening convection heat chamber or chambers with the intermediate passage, an outlet passage, and dampers for controlling communication of the final convection chamber with the outlet passage.

DONALD J. MOSSHART.

ROBERT A. FORESMAN. 

